Please 343, consider the effect a better ranking system woul have on the community. A system like Reach's is tired and overdone. Halo 3 had the right idea with a brutal and challenging way to rank up. It was tough, rewarding, and fun.
I loved seeing brigadiers and generals and actually knowing they had skill based on their rank. Unlike in Reach's system where even the highest ranked players are hardly formidable opponents. It just doesn't make sense.
Everyone wants something for nothing nowadays, don't give in to this new casual trend.